Message-ID: <Z2N0z5Is-Ab8uiGw@google.com>
Date: Thu, 19 Dec 2024 01:20:15 +0000
From: Benson Leung <bleung@...gle.com>
To: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
Cc: heikki.krogerus@...ux.intel.com, tzungbi@...nel.org,
	linux-usb@...r.kernel.org, chrome-platform@...ts.linux.dev,
	akuchynski@...gle.com, sboyd@...nel.org, pmalani@...omium.org,
	badhri@...gle.com, rdbabiera@...gle.com,
	dmitry.baryshkov@...aro.org, jthies@...gle.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/8] usb: typec: Add driver for Thunderbolt 3
 Alternate Mode

On Fri, Dec 13, 2024 at 03:35:43PM -0800, Abhishek Pandit-Subedi wrote:
> From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> 
> Thunderbolt 3 Alternate Mode entry flow is described in
> USB Type-C Specification Release 2.0.
> 
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Co-developed-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
> Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>

Reviewed-by: Benson Leung <bleung@...omium.org>

> ---
> 
> Changes in v5:
> - Add lockdep, missing includes and fix up block comment style.
> 
> Changes in v4:
> - Large refactor to use cable_altmodes
> - Fixed ordering of cable mode enter/exit (SOP', SOP", then port for
>   enter; reverse order for exit)
> - Other small fixes from v3 feedback
> 
> Changes in v3:
> - Revert rename of TYPEC_TBT_MODE
> - Remove mode from typec_device_id
> 
> Changes in v2:
> - Use <linux/usb/typec_tbt.h> and add missing TBT_CABLE_ROUNDED
> - Pass struct typec_thunderbolt_data to typec_altmode_notify
> - Rename TYPEC_TBT_MODE to USB_TYPEC_TBT_MODE
> - Use USB_TYPEC_TBT_SID and USB_TYPEC_TBT_MODE for device id
> - Change module license to GPL due to checkpatch warning
> 
> Changes in v1:
> - Delay cable + plug checks so that the module doesn't fail to probe
>   if cable + plug information isn't available by the time the partner
>   altmode is registered.
> - Remove unncessary brace after if (IS_ERR(plug))
> 
>  drivers/usb/typec/altmodes/Kconfig       |   9 +
>  drivers/usb/typec/altmodes/Makefile      |   2 +
>  drivers/usb/typec/altmodes/thunderbolt.c | 388 +++++++++++++++++++++++
>  include/linux/usb/typec_tbt.h            |   1 +
>  4 files changed, 400 insertions(+)
>  create mode 100644 drivers/usb/typec/altmodes/thunderbolt.c
> 
> diff --git a/drivers/usb/typec/altmodes/Kconfig b/drivers/usb/typec/altmodes/Kconfig
> index 1a6b5e872b0d..7867fa7c405d 100644
> --- a/drivers/usb/typec/altmodes/Kconfig
> +++ b/drivers/usb/typec/altmodes/Kconfig
> @@ -23,4 +23,13 @@ config TYPEC_NVIDIA_ALTMODE
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called typec_nvidia.
>  
> +config TYPEC_TBT_ALTMODE
> +	tristate "Thunderbolt3 Alternate Mode driver"
> +	help
> +	  Select this option if you have Thunderbolt3 hardware on your
> +	  system.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called typec_thunderbolt.
> +
>  endmenu
> diff --git a/drivers/usb/typec/altmodes/Makefile b/drivers/usb/typec/altmodes/Makefile
> index 45717548b396..508a68351bd2 100644
> --- a/drivers/usb/typec/altmodes/Makefile
> +++ b/drivers/usb/typec/altmodes/Makefile
> @@ -4,3 +4,5 @@ obj-$(CONFIG_TYPEC_DP_ALTMODE)		+= typec_displayport.o
>  typec_displayport-y			:= displayport.o
>  obj-$(CONFIG_TYPEC_NVIDIA_ALTMODE)	+= typec_nvidia.o
>  typec_nvidia-y				:= nvidia.o
> +obj-$(CONFIG_TYPEC_TBT_ALTMODE)		+= typec_thunderbolt.o
> +typec_thunderbolt-y			:= thunderbolt.o
> diff --git a/drivers/usb/typec/altmodes/thunderbolt.c b/drivers/usb/typec/altmodes/thunderbolt.c
> new file mode 100644
> index 000000000000..1b475b1d98e7
> --- /dev/null
> +++ b/drivers/usb/typec/altmodes/thunderbolt.c
> @@ -0,0 +1,388 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * USB Typec-C Thunderbolt3 Alternate Mode driver
> + *
> + * Copyright (C) 2019 Intel Corporation
> + * Author: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> + */
> +
> +#include <linux/lockdep.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/workqueue.h>
> +#include <linux/usb/pd_vdo.h>
> +#include <linux/usb/typec_altmode.h>
> +#include <linux/usb/typec_tbt.h>
> +
> +enum tbt_state {
> +	TBT_STATE_IDLE,
> +	TBT_STATE_SOP_P_ENTER,
> +	TBT_STATE_SOP_PP_ENTER,
> +	TBT_STATE_ENTER,
> +	TBT_STATE_EXIT,
> +	TBT_STATE_SOP_PP_EXIT,
> +	TBT_STATE_SOP_P_EXIT
> +};
> +
> +struct tbt_altmode {
> +	enum tbt_state state;
> +	struct typec_cable *cable;
> +	struct typec_altmode *alt;
> +	struct typec_altmode *plug[2];
> +	u32 enter_vdo;
> +
> +	struct work_struct work;
> +	struct mutex lock; /* device lock */
> +};
> +
> +static bool tbt_ready(struct typec_altmode *alt);
> +
> +static int tbt_enter_mode(struct tbt_altmode *tbt)
> +{
> +	struct typec_altmode *plug = tbt->plug[TYPEC_PLUG_SOP_P];
> +	u32 vdo;
> +
> +	vdo = tbt->alt->vdo & (TBT_VENDOR_SPECIFIC_B0 | TBT_VENDOR_SPECIFIC_B1);
> +	vdo |= tbt->alt->vdo & TBT_INTEL_SPECIFIC_B0;
> +	vdo |= TBT_MODE;
> +
> +	if (plug) {
> +		if (typec_cable_is_active(tbt->cable))
> +			vdo |= TBT_ENTER_MODE_ACTIVE_CABLE;
> +
> +		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_SPEED(plug->vdo));
> +		vdo |= plug->vdo & TBT_CABLE_ROUNDED;
> +		vdo |= plug->vdo & TBT_CABLE_OPTICAL;
> +		vdo |= plug->vdo & TBT_CABLE_RETIMER;
> +		vdo |= plug->vdo & TBT_CABLE_LINK_TRAINING;
> +	} else {
> +		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_USB3_PASSIVE);
> +	}
> +
> +	tbt->enter_vdo = vdo;
> +	return typec_altmode_enter(tbt->alt, &vdo);
> +}
> +
> +static void tbt_altmode_work(struct work_struct *work)
> +{
> +	struct tbt_altmode *tbt = container_of(work, struct tbt_altmode, work);
> +	int ret;
> +
> +	mutex_lock(&tbt->lock);
> +
> +	switch (tbt->state) {
> +	case TBT_STATE_SOP_P_ENTER:
> +		ret = typec_cable_altmode_enter(tbt->alt, TYPEC_PLUG_SOP_P, NULL);
> +		if (ret) {
> +			dev_dbg(&tbt->plug[TYPEC_PLUG_SOP_P]->dev,
> +				"failed to enter mode (%d)\n", ret);
> +			goto disable_plugs;
> +		}
> +		break;
> +	case TBT_STATE_SOP_PP_ENTER:
> +		ret = typec_cable_altmode_enter(tbt->alt, TYPEC_PLUG_SOP_PP,  NULL);
> +		if (ret) {
> +			dev_dbg(&tbt->plug[TYPEC_PLUG_SOP_PP]->dev,
> +				"failed to enter mode (%d)\n", ret);
> +			goto disable_plugs;
> +		}
> +		break;
> +	case TBT_STATE_ENTER:
> +		ret = tbt_enter_mode(tbt);
> +		if (ret)
> +			dev_dbg(&tbt->alt->dev, "failed to enter mode (%d)\n",
> +				ret);
> +		break;
> +	case TBT_STATE_EXIT:
> +		typec_altmode_exit(tbt->alt);
> +		break;
> +	case TBT_STATE_SOP_PP_EXIT:
> +		typec_cable_altmode_exit(tbt->alt, TYPEC_PLUG_SOP_PP);
> +		break;
> +	case TBT_STATE_SOP_P_EXIT:
> +		typec_cable_altmode_exit(tbt->alt, TYPEC_PLUG_SOP_P);
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	tbt->state = TBT_STATE_IDLE;
> +
> +	mutex_unlock(&tbt->lock);
> +	return;
> +
> +disable_plugs:
> +	for (int i = TYPEC_PLUG_SOP_PP; i > 0; --i) {
> +		if (tbt->plug[i])
> +			typec_altmode_put_plug(tbt->plug[i]);
> +
> +		tbt->plug[i] = NULL;
> +	}
> +
> +	tbt->state = TBT_STATE_ENTER;
> +	schedule_work(&tbt->work);
> +	mutex_unlock(&tbt->lock);
> +}
> +
> +/*
> + * If SOP' is available, enter that first (which will trigger a VDM response
> + * that will enter SOP" if available and then the port). If entering SOP' fails,
> + * stop attempting to enter either cable altmode (probably not supported) and
> + * directly enter the port altmode.
> + */
> +static int tbt_enter_modes_ordered(struct typec_altmode *alt)
> +{
> +	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
> +	int ret = 0;
> +
> +	lockdep_assert_held(&tbt->lock);
> +
> +	if (!tbt_ready(tbt->alt))
> +		return -ENODEV;
> +
> +	if (tbt->plug[TYPEC_PLUG_SOP_P]) {
> +		ret = typec_cable_altmode_enter(alt, TYPEC_PLUG_SOP_P, NULL);
> +		if (ret < 0) {
> +			for (int i = TYPEC_PLUG_SOP_PP; i > 0; --i) {
> +				if (tbt->plug[i])
> +					typec_altmode_put_plug(tbt->plug[i]);
> +
> +				tbt->plug[i] = NULL;
> +			}
> +		} else {
> +			return ret;
> +		}
> +	}
> +
> +	return tbt_enter_mode(tbt);
> +}
> +
> +static int tbt_cable_altmode_vdm(struct typec_altmode *alt,
> +				 enum typec_plug_index sop, const u32 hdr,
> +				 const u32 *vdo, int count)
> +{
> +	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
> +	int cmd_type = PD_VDO_CMDT(hdr);
> +	int cmd = PD_VDO_CMD(hdr);
> +
> +	mutex_lock(&tbt->lock);
> +
> +	if (tbt->state != TBT_STATE_IDLE) {
> +		mutex_unlock(&tbt->lock);
> +		return -EBUSY;
> +	}
> +
> +	switch (cmd_type) {
> +	case CMDT_RSP_ACK:
> +		switch (cmd) {
> +		case CMD_ENTER_MODE:
> +			/*
> +			 * Following the order described in USB Type-C Spec
> +			 * R2.0 Section 6.7.3: SOP', SOP", then port.
> +			 */
> +			if (sop == TYPEC_PLUG_SOP_P) {
> +				if (tbt->plug[TYPEC_PLUG_SOP_PP])
> +					tbt->state = TBT_STATE_SOP_PP_ENTER;
> +				else
> +					tbt->state = TBT_STATE_ENTER;
> +			} else if (sop == TYPEC_PLUG_SOP_PP)
> +				tbt->state = TBT_STATE_ENTER;
> +
> +			break;
> +		case CMD_EXIT_MODE:
> +			/* Exit in opposite order: Port, SOP", then SOP'. */
> +			if (sop == TYPEC_PLUG_SOP_PP)
> +				tbt->state = TBT_STATE_SOP_P_EXIT;
> +			break;
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	if (tbt->state != TBT_STATE_IDLE)
> +		schedule_work(&tbt->work);
> +
> +	mutex_unlock(&tbt->lock);
> +	return 0;
> +}
> +
> +static int tbt_altmode_vdm(struct typec_altmode *alt,
> +			   const u32 hdr, const u32 *vdo, int count)
> +{
> +	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
> +	struct typec_thunderbolt_data data;
> +	int cmd_type = PD_VDO_CMDT(hdr);
> +	int cmd = PD_VDO_CMD(hdr);
> +
> +	mutex_lock(&tbt->lock);
> +
> +	if (tbt->state != TBT_STATE_IDLE) {
> +		mutex_unlock(&tbt->lock);
> +		return -EBUSY;
> +	}
> +
> +	switch (cmd_type) {
> +	case CMDT_RSP_ACK:
> +		/* Port altmode is last to enter and first to exit. */
> +		switch (cmd) {
> +		case CMD_ENTER_MODE:
> +			memset(&data, 0, sizeof(data));
> +
> +			data.device_mode = tbt->alt->vdo;
> +			data.enter_vdo = tbt->enter_vdo;
> +			if (tbt->plug[TYPEC_PLUG_SOP_P])
> +				data.cable_mode = tbt->plug[TYPEC_PLUG_SOP_P]->vdo;
> +
> +			typec_altmode_notify(alt, TYPEC_STATE_MODAL, &data);
> +			break;
> +		case CMD_EXIT_MODE:
> +			if (tbt->plug[TYPEC_PLUG_SOP_PP])
> +				tbt->state = TBT_STATE_SOP_PP_EXIT;
> +			else if (tbt->plug[TYPEC_PLUG_SOP_P])
> +				tbt->state = TBT_STATE_SOP_P_EXIT;
> +			break;
> +		}
> +		break;
> +	case CMDT_RSP_NAK:
> +		switch (cmd) {
> +		case CMD_ENTER_MODE:
> +			dev_warn(&alt->dev, "Enter Mode refused\n");
> +			break;
> +		default:
> +			break;
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	if (tbt->state != TBT_STATE_IDLE)
> +		schedule_work(&tbt->work);
> +
> +	mutex_unlock(&tbt->lock);
> +
> +	return 0;
> +}
> +
> +static int tbt_altmode_activate(struct typec_altmode *alt, int activate)
> +{
> +	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
> +	int ret;
> +
> +	mutex_lock(&tbt->lock);
> +
> +	if (activate)
> +		ret = tbt_enter_modes_ordered(alt);
> +	else
> +		ret = typec_altmode_exit(alt);
> +
> +	mutex_unlock(&tbt->lock);
> +
> +	return ret;
> +}
> +
> +static const struct typec_altmode_ops tbt_altmode_ops = {
> +	.vdm		= tbt_altmode_vdm,
> +	.activate	= tbt_altmode_activate
> +};
> +
> +static const struct typec_cable_ops tbt_cable_ops = {
> +	.vdm		= tbt_cable_altmode_vdm,
> +};
> +
> +static int tbt_altmode_probe(struct typec_altmode *alt)
> +{
> +	struct tbt_altmode *tbt;
> +
> +	tbt = devm_kzalloc(&alt->dev, sizeof(*tbt), GFP_KERNEL);
> +	if (!tbt)
> +		return -ENOMEM;
> +
> +	INIT_WORK(&tbt->work, tbt_altmode_work);
> +	mutex_init(&tbt->lock);
> +	tbt->alt = alt;
> +
> +	alt->desc = "Thunderbolt3";
> +	typec_altmode_set_drvdata(alt, tbt);
> +	typec_altmode_set_ops(alt, &tbt_altmode_ops);
> +
> +	if (tbt_ready(alt)) {
> +		if (tbt->plug[TYPEC_PLUG_SOP_P])
> +			tbt->state = TBT_STATE_SOP_P_ENTER;
> +		else if (tbt->plug[TYPEC_PLUG_SOP_PP])
> +			tbt->state = TBT_STATE_SOP_PP_ENTER;
> +		else
> +			tbt->state = TBT_STATE_ENTER;
> +		schedule_work(&tbt->work);
> +	}
> +
> +	return 0;
> +}
> +
> +static void tbt_altmode_remove(struct typec_altmode *alt)
> +{
> +	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
> +
> +	for (int i = TYPEC_PLUG_SOP_PP; i > 0; --i) {
> +		if (tbt->plug[i])
> +			typec_altmode_put_plug(tbt->plug[i]);
> +	}
> +
> +	if (tbt->cable)
> +		typec_cable_put(tbt->cable);
> +}
> +
> +static bool tbt_ready(struct typec_altmode *alt)
> +{
> +	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
> +	struct typec_altmode *plug;
> +
> +	if (tbt->cable)
> +		return true;
> +
> +	/* Thunderbolt 3 requires a cable with eMarker */
> +	tbt->cable = typec_cable_get(typec_altmode2port(tbt->alt));
> +	if (!tbt->cable)
> +		return false;
> +
> +	/* We accept systems without SOP' or SOP''. This means the port altmode
> +	 * driver will be responsible for properly ordering entry/exit.
> +	 */
> +	for (int i = 0; i < TYPEC_PLUG_SOP_PP + 1; i++) {
> +		plug = typec_altmode_get_plug(tbt->alt, i);
> +		if (IS_ERR(plug))
> +			continue;
> +
> +		if (!plug || plug->svid != USB_TYPEC_TBT_SID)
> +			break;
> +
> +		plug->desc = "Thunderbolt3";
> +		plug->cable_ops = &tbt_cable_ops;
> +		typec_altmode_set_drvdata(plug, tbt);
> +
> +		tbt->plug[i] = plug;
> +	}
> +
> +	return true;
> +}
> +
> +static const struct typec_device_id tbt_typec_id[] = {
> +	{ USB_TYPEC_TBT_SID },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(typec, tbt_typec_id);
> +
> +static struct typec_altmode_driver tbt_altmode_driver = {
> +	.id_table = tbt_typec_id,
> +	.probe = tbt_altmode_probe,
> +	.remove = tbt_altmode_remove,
> +	.driver = {
> +		.name = "typec-thunderbolt",
> +	}
> +};
> +module_typec_altmode_driver(tbt_altmode_driver);
> +
> +MODULE_AUTHOR("Heikki Krogerus <heikki.krogerus@...ux.intel.com>");
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Thunderbolt3 USB Type-C Alternate Mode");
> diff --git a/include/linux/usb/typec_tbt.h b/include/linux/usb/typec_tbt.h
> index fa97d7e00f5c..55dcea12082c 100644
> --- a/include/linux/usb/typec_tbt.h
> +++ b/include/linux/usb/typec_tbt.h
> @@ -44,6 +44,7 @@ struct typec_thunderbolt_data {
>  
>  #define   TBT_GEN3_NON_ROUNDED                 0
>  #define   TBT_GEN3_GEN4_ROUNDED_NON_ROUNDED    1
> +#define TBT_CABLE_ROUNDED		BIT(19)
>  #define TBT_CABLE_OPTICAL		BIT(21)
>  #define TBT_CABLE_RETIMER		BIT(22)
>  #define TBT_CABLE_LINK_TRAINING		BIT(23)
> -- 
> 2.47.1.613.gc27f4b7a9f-goog
> 
> 

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